Author Topic: Main Thrust bearings (Read 12251 times)

SoupieMelody · « **on:** December 14, 2009, 05:32:44 AM »

Okay my issue is that there is play in the crankshaft keeps going in and out. Today the altenator belt fell off. Is it worth it to replace those bearings or replace the engine ? It's a BMW 1991 e30 318i sedan with m42 engine

ck_carnut · « **Reply #1 on:** December 14, 2009, 12:18:22 PM »

If your thrust bearings are worn to the point that you have significant play, you've probably got big problems internally.

How did you diagnose the play in the crank. How far is it moving?

SoupieMelody · « **Reply #2 on:** December 14, 2009, 06:04:07 PM »

Quote from: ck_carnut;83005

If your thrust bearings are worn to the point that you have significant play, you've probably got big problems internally.

How did you diagnose the play in the crank. How far is it moving?

well i just look at it from sight and used a screw driver and it moved about .25 inch

1991 E30 M42 · « **Reply #3 on:** December 15, 2009, 12:54:56 AM »

If it moves that much I think your thrust bearing are MIA as I do not think the combined thickness of them are a 1/4", check to make sure your crank pulley is tight, there is a center bolt that holds the hub to the crank and requires somewhere around 200ft/lbs (i think) and there are several that join the hub to the actual pulleys.

ck_carnut · « **Reply #4 on:** December 15, 2009, 08:46:48 AM »

Quote from: SoupieMelody;83026

well i just look at it from sight and used a screw driver and it moved about .25 inch

That's huge! I don't know the exact BMW spec, but that thrust distance should be less than .010 inch or so.

As above, check the pulley first. If it's tight, then you've got bigger issues.

I'll bet if you drop your oil pan (difficult on these motors in the car, I know) you'll find the thrust wahers there. If you're lucky, you haven't trashed the crank/block yet.

quinn11m20 · « **Reply #5 on:** December 15, 2009, 04:49:49 PM »

Yeah, sounds like some more serious issues. By the way, If you want to keep your car then its worth it to get it properly repaired.

DesktopDave · « **Reply #6 on:** December 15, 2009, 06:32:30 PM »

Definitely big problems there. I'd pull the crank pulley & hope that the woodruff key (part 9 here) has broken. If the crank nose is cracked it'd cause trouble like you mention. Happened to an old Nissan of mine; I overtorqued the crank pulley & cracked the crank nose. That was a cast shaft, not forged like our trusty M42.

Looking at that diagram it looks like there are lots of places for off-center pulleys, don't condemn the engine just yet...might be perfectly good as-is with a few cracked bolts or a bent/pinched pulley.

SoupieMelody · « **Reply #7 on:** December 16, 2009, 06:04:20 PM »

ok thanks for the help and advices guys...the pulleys are fine...well today my mechanic and i took down the whole thing and one of the thrust washer wasnt there...i had ordered a set of main and con rod std bearings from pelicanparts.com and we installed them...everything is going well so far....changed the oil, filter, sparks plug and fuel filter, ICV and the car feels way better now

DesktopDave · « **Reply #8 on:** December 16, 2009, 06:42:33 PM »

I'm surprised the car ran like that...glad it didn't kill the engine.

The real question on my mind is...what the heck was the PO doing? Or was some shady mechanic tossing it back together? Maybe back in 1990 the Bavarian engine assembly guy was having a bad day?

nickmpower · « **Reply #9 on:** December 16, 2009, 06:46:34 PM »

the m42 only has 180 degree thrust surface stock.

SoupieMelody · « **Reply #10 on:** December 17, 2009, 02:46:18 AM »

Quote from: DesktopDave;83106

I'm surprised the car ran like that...glad it didn't kill the engine.

The real question on my mind is...what the heck was the PO doing? Or was some shady mechanic tossing it back together? Maybe back in 1990 the Bavarian engine assembly guy was having a bad day?

Lol that's what I'm saying. Like when we removed them, you could see the lining where the washer should have been at compare to the other one... Glad that's fixed and over with hopefully I don't have anymore issues for a long time

ck_carnut · « **Reply #11 on:** December 17, 2009, 09:11:01 AM »

Quote from: nickmpower;83107

the m42 only has 180 degree thrust surface stock.

The old Triumph 1300/1500 engines used in Spitfires from the 60's and 70's (and MG Midget 1500s like mine in the late 70's) had this design, and these engines were notorious for dropping thrush washers into the pan. I'm very surprised BMW would have gone with this kind of design.

One thing a lot of Triumph guys do is pin the thrust washers in place so that when they do wear, they don't drop into the sump and cause crank/main bearing cap damage. When I refreshed my 1500, I used a red Loctite to keep them in place. So far, so good.

The other thing we do is keep our foot off the clutch pedal as much as possible (i.e. don't keep the pedal pushed in at a red light).

waldo · « **Reply #12 on:** December 23, 2009, 07:46:00 PM »

I am curious since this is not something I know a lot about but want to learn.

I would conclude that according to this:
http://www.pelicanparts.com/cgi-bin/smart/more_info.cgi?pn=11-21-1-706-829-BOE&catalog_description=BEARING%20SHELL
all of those BMW inline engines also only have 180 degrees of thrust.

What is the difference between yellow, green, and white?
http://www.realoem.com/bmw/showparts.do?model=AF93&mospid=47305&btnr=11_0292&hg=11&fg=20

What would prevent one from using two thrust bearings for 360 degrees? The bearing sets on Pelican show 2 bearings per set, so I thinking this is an after thought.

Where are the thrust washers?

wannam42 · « **Reply #13 on:** December 30, 2009, 11:22:56 PM »

bumpity because I want to know too

nickmpower · « **Reply #14 on:** December 31, 2009, 12:29:58 AM »

if you get an aftermarket set it will come with a 360 degree bearing. Someone should PM Peerless and ask him what bearings he uses